Lap-top computers, because of their portability, have rapidly gained popularity. This type of computer usually incorporates a battery, which enables them to be operative anywhere irrespective of availability of an electrical power supply outlet, e.g., a wall outlet. Rechargeable battery packs are designed to be removably mounted in such computers, along with connectors to connect such battery packs to the main bodies of the computers. In general, this type of battery pack has only a plurality of electrically conductive pads (hereinafter referred to as "conductive pads") for electrical connection on the surface, and a mating connector engages with these conductive pads to establish electrical connection. This type of connector has been in use and known as "surface-contact connector".
Main roles of such battery pack are to supply electrical power to the computer in one direction and to receive electrical power for recharging itself in the other direction. However, there is a type of battery pack which includes a sensor to detect changes in the temperature during recharging process. In this battery pack, signals from this temperature sensor are conveyed to the computer through one of the conductive pads to control the supply of recharging power. Yet, there is another type of battery pack which further includes a CPU to estimate the amount of remaining charge and to control the recharging and discharging of the cells. Signals used for this control are conveyed through some of the conductive pads of the battery pack.
Here, it is clear that a surface-contact connector which is to be used for connecting such battery pack must include a plurality of terminals in correspondence with the number of conductive pads provided on the battery pack. For this reason, surface-contact connectors are generally designed in the following manner. A row of terminals, each terminal having a contacting portion, are retained in a housing to construct a surface-contact connector so that the contacting portions protrude from the housing in a row. When the battery pack is inserted or mounted into the main body of the computer, the contacting portion of each terminal of the connector is brought into engagement with a corresponding conductive pad of the battery pack to establish electrical connection.
In this type of surface-contact connector of the prior art, all the terminals are formed in an identical shape. Thus, when they are retained in the housing, the contacting portions of the terminals have the same amount of protrusion. Therefore, when the battery pack is inserted into a respective position, all the terminals of the surface-contact connector are brought into engagement with the conductive pads of the battery pack, simultaneously.
This type of surface-contact connector presents a problem when such a connector is used for a battery pack which is designed not only for charging and discharging electrical power but also for transmitting various control signals through conductive pads as previously mentioned (i.e., some conductive pads are used for connecting signal transmission in addition to a conductive pad for connecting electrical power supply). If all the conductive pads of this battery pack are brought into engagement with the terminals of the connector simultaneously as practiced in the prior art, noise caused from the power line may get onto a signal line, or even worse, discharge from the power supply may come onto a signal line and may damage an electronic device, e.g., CPU, which is connected to the signal line.
Therefore, it is desired that a power line, a grounding line, and signal lines be connected sequentially with some time differences (connection carried out in this way is hereinafter referred to as "sequential connection") while the battery pack is inserted. It is possible to achieve this sequential connection by forming the terminals of the connector in various shapes so that each terminal comes into engagement with a corresponding conductive pad of the battery pack at a different position specific to the individual terminal. However, this approach involves use of several types of terminals, which certainly increases the production cost of the connector as well as the inventory cost of the terminals.